1. Field of the Invention
This invention relates to a detachable and attachable sheet tray for a printing device. The sheet tray includes a sheet setting board on which a plurality of sheets are set. The sheet setting board is moved up and down by a linkage between a first linkage member in the sheet tray and a second linkage member in the printing device. The position of the second linkage member is adjusted corresponding to the position of the first linkage member while the sheet tray is detached from the printing device.
2. Description of the Background Art
To make use of a printing device easier for a user with disabilities, section 508 of the Rehabilitation act has been established. The regulation requires “products which have mechanically operated controls or keys shall comply with the following: Controls and keys shall be operable with one hand and shall not require tight grasping, pinching, twisting of the wrist. The force required to activate controls and keys shall be 5 lbs. (22.2N) maximum”.
But so far in conventional printing devices, this regulation has not been significantly considered. Therefore, the force for setting a sheet tray into a printing device sometimes exceeds the noted regulation.
Typical printing devices of this type are disclosed, for instance, in Japanese Patent No. 3176455 and Japanese Open-Laid Patent H07-196174.
Printing devices of this type include sheet trays that have to be pulled out from a printing device to add some sheets. After sheets are supplied, the sheet tray is pushed back into the printing device. A sheet setting board is provided at a side of such a sheet tray on which a plurality of sheets are set. The sheet setting board has a shaft at the opposite side of the sheet feeding direction. The shaft is linked to a coupling in the printer device by a pin attached to the shaft and a groove on the coupling. A motor in the printing device rotates the coupling, and the coupling conveys the rotation to the shaft through the linkage. With the rotation of the shaft, the sheet setting board makes a pivot movement. By pivoting around the shaft, the sheet setting board is moved up and the position of the uppermost sheet of the plurality of the sheets on the paper setting board is maintained regardless of the amount of remaining sheets.
Detachment between the sheet tray and the printing device occurs between the pin and the groove. After the pin is detached from the groove the sheet setting board goes down by its weight, but if a position of the coupling is not controlled that causes a position inconsistence between the pin and the coupling.
If the sheet tray is pushed into the printing device under that condition, the pin collides with the coupling. The coupling is fixed to a motor shaft with a spring and can move parallel to the motor shaft. Therefore, the coupling is pushed and moves to the printing device. As a result, the position difference requires more power to push in the sheet tray to the printing device for operators.